Trip-free overload circuit breaker



Nov. 15, 1960 M. B. WOOD 2,950,587

TRIP-FREE ovERLoAD CIRCUIT BREAKER Filed Jan. 1s, 1959 Inventor Mor-ris .BAW/'ood B y his Attorney i States Patent O M FEW-.e PEE @VERLQAD CIRCUIT BREAKER Morris E. Wood, Newburyport, Mass., assigner to Wood 1., intestine Corporation, Lynn, Mass., a corporation of Massachusetts Filed `ian. 13, 1959, Ser. No. 736,644

12 Claims. (Cl. 20G-116) The present invention relates to improvements in electrical circuit breakers of the trip-free type, more particulai-ly as disclosed in an application for United States Letters Patent Ser. No. 774,774, filed Nov. 18, 1958, in the name of the present inventor, in which an extremely cornpact and reliably operating construction having two sets of contacts is provided for introducing a double break interruption in a circuit instead of a single break in -accordance with conventional practice.

in the invention of the prior application compactness of construction is made possible by the use of a split rectangular frame formed with `a pair of opposed hollow insulating shells and by a unique system for assembly of the breaker, including unitized movable contact elements brought together outside the shells and introduced therein simultaneously with alinement into opposed relationship. The ease with which the final steps of assembly are accomplished for that breaker is entirely dependent upon the accuracy with which the contact elements are manufactured and upon the freedom from distortion incident to formation of the shells, ordinarily shaped by molding.

An object of the present invention is to provide a breaker of the type referred to, which may be assembled readily when there are substantial variations in dimensions in the individual contact elements and a limited amount of distortion in a surrounding insulating. frame containing them. Other objects are to provide a trip-free circuit breaker of simple, relatively easily assembled design whi-le retaining all of the advantages in compactness, in reliability and in yother respects at least to the extent found in the breaker of the prior application, above identified. To attain these objects a novel and simplified form of movable contact support and an improved twopart telescoping frame are employed, rather than the opposed shells in the frame of the breaker disclosed in the prior application.

These and other features of the invention, as hereinafter described and claimed will readily be apparent to those skilled in the art, from the following detailed description taken in connection with the accompanying drawings, in which:

Fig. l is a sectional side View of a trip-free automatically reset circuit breaker embodying the features of the present invention with the contacts in circuit opening positions;

Fig. 2 is a similar view of the circuit breaker shown in Fig. l with the contacts thereof in closed circuit positions;

Fig. 3 is a sectional View of the circuit breaker taken along the line III- HI of Fig. 2; and

Fig. 4 is a sectional plan View of the breaker taken along the line IV--IV of Fig. 2.

The trip-free overload circuit breaker illustrated in the drawings is manually operated to close or open a circuit to be controlled and is actuated automatically to open and to prevent holding the circuit closed under conditions of overload until the conditions are corrected.

Patented Nov. i5, i960 The mechanism for actuating the breaker contacts is the same in many respects as that of the prior application, in that a locked releasable member and a Contact actuating member are moved yieldingly together and are separated from each other to close the circuit to be controlled, by a wedging member connected to a manually operable button projecting from the breaker.

Except as hereinafter `described the illustrated circuit breaker is substantially the same as that disclosed in the application noted above. The contacts are Iarranged to open the circuit at two points connected in series, so that less arcing will occur. To assist in opening the contacts resilient means acts on the separable members to urge them together.

Instead of utilizing a pair 0f opposed hollow shells for a frame, the present breaker has a two-part insulating frame, the outer part of which is indicated at 10. The frame parts are constructed to telescope, in the inner one sliding within the outer one 10. With the exception of the manually operable button, indicated at 12, all of the functional parts are mechanically mounted within the inner casing. The button 12 is mounted to slide centrally in a lengthwise direction in a sleeve portion of the outer casing 10.

The inner casing consists of two parallel insulating plates 14 land 16 (Figs. 3 and 4) between which are fixed a pair of spaced contacts 18 and 20. To hold the fixed contacts in place they are welded to a terminal strip 22 and to one end of a Z-shaped connector strap 24. The other end of the connector strap is secured to `a thermostatic latch 26 for locking the locked and releasable separable member, indicated at 28. The connecting portion of the Z-shaped strap has its central area cut out and along the edges of the central area the strap is fastened to the plates 14 and 16 to assist in holding them together. The terminal strip 22 is similarly fastened along its edges to the inner casing plates 14 and 16 and passes through a slot in an insulating base 30, fitting between the plates 14 and 16 and closing the lower end of the outer casing 10. The base 30 also has a second slot through which passes a second terminal strip 32 similarly fastened to the side plates of the inner casing.

To fasten the terminal strips 22 and 32 and the Z-shaped connector strap 24 to the side plates 14 and 16 their edges have oppositely projecting tongues 34, fitting within rectangular holes in the side plates, the tongues being riveted over outside the plates to hold them in place. The terminal strips 22 and 3-2 have enlargements outside the base block 30, in which binding screws 36 are threaded and shoulders on these enlargements hold the base 30 securely against the lower edges of the inner casing plates when the tongues on the terminal strips are riveted over the side plates. Thus, the inner casing has three sides open and its lower side closed by the base 30.

The outer casing 10 is formed of molded resinous material having its upper end provided with the sleeve portion indicated at 33, in which the actuating button 12 slides and a pair of perforated mounting lugs 40 for attaching the breaker to a panel. To secure together the inner and outer casings, the base 30 and outer casing have similarly shaped enlargements 42 and ears 44, which are perforated to receive a fastening pin 46 extending through the lower ends of the telescoping casings crosswise to, and in line with, the length of the actuating button. By arranging the pin 46 in this way the forces applied to the button in actuating the circuit breaker cause no lateral forces on the sides of the telescoping casings, tending to Wrack or wear them. All of the forces applied to the button are `accordingly directed against the pin and are expanded in opening or closing the contacts with the least possible friction.

The locked releasable member 28 includes the rst of the separable members, in the form of an abutment roll 4S rotatable on a rivet 50 connecting two sides of the locked member formed as a double lever. The roll is held between the sides of the lever and the lever is fulcrumed on a pin 52 passing through a slot 54 in the lever, the ends of the pin being riveted to the inner casing pla-tes 14 and 16. To lock the releasable member an arm of the member 28, is engaged beneath its end by a block 56 on the thermostatic latch 26.

To adjust the thermostatic latch, the inner casing has a cross plate 58 extending between rectangular notches in the side plates 14 and 16. Passing through the cross plate is a countersunk screw 60, extending through a clearance opening in the thermostatic latch. The shank of the screw is threaded into an arm 62 welded to the same end of the connector strap to which the thermostatic latch is secured. The head of the screw is engaged in the cross plate of the inner casing, so that after the outer casing lll is telescoped with the inner casing the adjusting screw is concealed. Thus, the thermostatic latch may be adjusted before the outer casing is applied and after complete assembly of the frame further adjustment will be discouraged.

The lower end of the thermostatic latch is connected to a flexible lead 64, also connected to the terminal strip 32. The circuit through the `breaker passes from the terminal strip 32 the flexible lead 64 the thermostatic latch 26, and the connector strap 24, to the lixed contacts 1S and 20 and the terminal strip 22. While the circuit is closed the fixed contacts 18 and 2i) are bridged by a bar 66 having movable contacts 68 and 70 carried thereby. The bridging bar is constructed from a length of resilient flat wire formed with a V-shape to enable it to press yieldlingly against the fixed contacts. As the movable contacts 68 and 70 engage the xed contacts the bridging bar exes and the movable contcats wipe the surfaces of the fixed contacts and break up oxide or other scale which might interfere with ow of current. However desirable this yaction may be, the greatest wiping movement occurs when the movable contacts first engage the fixed contacts and as heavier pressure is applied the wiping movement diminishes.

The feature of the invention relating to a novel form of contact support consists in mounting the bridging bar 66 in a manner to increase the wiping movement instead of diminishing it, as the contact pressure becomes heavier. The oxide scale is more readily broken up and the contact surfaces are kept cleaner under these conditions. Such results are particularly desirable with a trip-free circuit breaker of the type employing a thermostatic latch, in which the response to excessive currents may be sluggish and from which relatively light forces only are available for tripping a circuit breaker.

The illustrated movable contact support consists of a leaf spring 72, hin-ged at one end to the frame, slidingly retained against movement toward the fixed contacts at the other end, and connected tothe bridging bar for movement toward and from the fixed contacts at its midportion. To hinge the leaf spring its upper end is wrapped about a rivet 74 secured between the inner casing plates 14 and i6. At the lower end of the leaf spring it engages a rivet 76 also secured in the inner casing plates. To connect the leaf spring 72 to the bridging bar v66 the contact actuating member is in the form of an enlarged head 78 on a fastener for securing the bridging bar to the leaf spring 72.

The head 78 comprises the second separable member, the first of which is the abutment roll 48. As the bridging bar moves from the position of Fig. 1 to that of Fig. 2 it is evident that it changes its shape from a V to a straight line, producing a decreasing wiping action with an increase in pressure. At the same time the leaf spring contact mounting moves from a straight line position to a bowed position, while swinging about the rivet 4 72. (See Fig. 2.) The bowing movement of the spring increases with the contact pressure and, accordingly the contact wiping action similarly increases in the direction of the arrows in Fig. 2.

To enable the forces exerted by the button 12 on the contact operating mechanism to be kept in line with the center of the breaker frame across the thickness of the frame the lower end of the button passes through the cut-out in the connector strap 24. Below the connector strap the button is pivotally connected to the upper end of a two part link 80. The lower end of the link is connected to the wedging member, in the form of a roll 82 rotatably mounted on a pin 84 having its ends secured in the parts of the link 80. The button 12 is so mounted that it slides between the bridging bar with its mounting spring 72 and the thermostatic latch 26, thus utilizing the space in the frame to best advantage.

The resilient means for opening the contacts consists of the movable contact supporting leaf spring 72 and the resilient bridging bar `66, which supplements the spring '72 in a part of the opening movement. To insure that the button is forced toward circuit opening position when the member 28 is unlatched a wire torsion spring 86 is coiled about the pin 52. The spring 86 is engaged at its midlength with the underside of the member 28 and at its ends with the terminal strip 32, which is bent at right angles to form a reliable bearing surface for the spring 86. When the member 28 is unlatchcd the abutment roll 48 moves below the level of the pin 48 and squeezes the wedging roll upwardly from between the abutment roll 48 and the fastener head 7S.

The nature and scope of the invention having been indicated and a particular embodiment having been described, what is claimed is:

l. A double break trip-free circuit breaker having an insulating frame, a pair of contacts fixed in the frame, a bridging bar for connecting the fixed contacts, a pair of separable members, a manually operable wedging member acting between the separable members to separate them, resilient means for moving the separable members together, a thermostatic latch for locking the first of the separable members against movement away from the second, a link connected at one end to the wedging member, and a button connected to the other end of the link and slidingly mounted in the frame between the bridging bar and the thermostatic latch, in combination with a support for the bridging bar comprising a leaf spring hinged to the frame at one end, slidingly retained against movement toward the xed contacts at the other end, and connected at its midportion to said second separable member and the bridging bar mounted for movement toward and from the fixed contacts to close and open the circuit therethrough.

2. A double break trip-free circuit breaker having an insulating frame, a pair of contacts fixed in the frame, a bridging bar for connecting the fixed contacts, a pair of separable members, a manually operable wedging member acting between the separable members to separate them, resilient means for moving the separable members together, a thermostatic latch for locking the first of the separable members against movement away from the second, a link connected at one end to the wedging member, a button connected to the other end of the link and slidingly mounted in the frame between the bridging bar and the thermostatic latch, in combination with a leaf spring on a midportion of which the second separable member and the bridging -bar are mounted for movement toward and from the fixed contacts to close and open the circuit therethrough, a hinge pin in the frame about which one end of the spring is wrapped and a second pin in the frame along which the other end of the spring is slidingly engaged to retain both ends of the spring against movement relative to the fixed contacts while being moved along its midportion toward Va or from the fixed contacts with a sliding action between the bridging bar and the fixed contacts.

3. A double break trip-free circuit breaker having an insulating frame, a pair of contacts fixed in the frame, a bridging bar for connecting the fixed contacts, a pair of separable members, a manually operable wedging member acting between the separable members to separate them, resilient means for moving the separable members together, a thermostatic latch for locking the first of the separable members against movement away from the second, a link connected at one end to the wedging member, a button connected to the other end of the link and slidingly mounted in the frame between the bridging bar and the thermostatic latch, in combination with a resilient leaf spring on a midportion of which said second separable member and the bridging bar are mounted for movement toward and from the fixed contacts to close and open the circuit therethrough, a hinge pin in the frame about which one end of the spring is rotatably mounted, a second pin in the frame along which the other end of the spring is slidingly engaged to retain both ends of the spring against movement relative to the fixed contacts while being moved along its midportion toward the xed contacts with a sliding action between the bridging bar and the tixed contacts, increasing with the pressure on the contacts as the movable contacts reach a final seating position on the fixed contacts.

4. A double break trip-free circuit breaker having an insulating frame, a pair of contacts tixed in the frame, a bridging bar for connecting the fixed contacts, a pair of separable members, a manually operable wedging member acting between the separable members to separate them, resilient means for moving the separable members together, a thermostatic latch for locking the first of the separable members against movement away from the second, a link connected at one end to the wedging member, a button connected to the other end of the link and slidingly mounted in the frame between the bridging bar and the thermostatic latch, and a support for the bridging bar in the frame, in combination with a Z- shaped connector strap at one end of which one fixed contact is secured, at the other end of which the thermostatic latch is secured and a central area of which is cut out and fastened to the frame with the button passing through the cut-out.

5. A double break trip-free circuit breaker having an insulating frame, a pair of contacts fixed in the frame, a bridging bar for connecting the tixed contacts, a pair of separable members, a manually operable wedging member acting between the separable members to separate them, resilient means for moving the separable members together, a thermostatic latch for locking the first of the separable members against movement away from the second, a link connected at one end to the wedging member, a button connected at the other end of the lnk and slidingly mounted in the frame between the bridging bar and the thermostatic latch, and a support for the bridging bar in the frame, in combination with a Z-shaped connector strap at one end of which the thermostatic latch is secured and a central area of which is cut out and formed with opposed tabs projecting into the sides of the frame to fasten the connector strap in the frame with the button passing through the cut-out in the strap between the link and the sliding mounting for the button in the frame, and an adjusting screw mounted in the frame and arranged to bend the thermostat securing end of the connector strap.

6. A double break trip-free circuit breaker having yan insulating frame, a pair of contacts in the frame, a bridging bar for connecting the xed contacts, a pair of separabale members, a manually operable wedging member acting between the separable members to separate them, resilient means for moving the separable members together, a thermostatic latch for locking the first of the separable members against movement away from the second, a link connected at one end to the wedging member, a button connected to the other end of the link and slidingly mounted in the frame between the bridging bar and the thermostatic latch and a support for the bridging bar in the frame, in combination with a connector strap, `at one end of which one fixed contact is secured, at the other end of which the thermostatic latch is secured and a central area of which is cut out and formed with opposed tabs projecting into spaced sides of the frame to fasten the connector strap in the frame, the button passing through the cut out in the strap between the link and the sliding mounting for the button in the frame, an adjusting screw mounted in the frame and an arm engaged by `the screw to bend the thermostatic latch securing end of the connector strap.

7. A trip-free circuit breaker having an insulating frame, a contact xed in the frame, a bridging bar for connecting the tixed contact, a pair of separable member a manually operable wedging member acting between the separable members to separate them, resilient means for moving the separable members together, la thermostatic latch for locking the ii-rst of the separable members against movementfaway from the second, a link connected at one end to the wedging member, a button connected to the other endof the link and silidingly mounted in the frame between the bridging bar and the thermostatic latch, and a support for the bridging bar in the frame, in combination with a connector strap at one end of which the tixed contact is secured, at the other end of which the. thermostatic latch is secured and a central area of which is cut out and fastened in the frame with the button passing through the cut-out and means for adjusting the thermostat'c latch comprising a screw extending parallel to the thermostatic latch, having its head engaged in the frame and an arm secured to the thermostatic latch through which shank portion of the screw is threaded to bend the connector strap.

8. A trip-free circuit breaker having an insulating frame, a contact iixed in the frame, a bridging bar for connecting the fixed contact, a pair of separable members, a manually operable wedging member acting between the separable members to separate them, res'lient means for moving the separable members together, a thermostatic latch for locking the tirst of the separable members against movement away from the second, a link connected at one end to the wedging member, a button connected to the other end of the link and slidingly mounted in the frame between the bridging bar and the thermostatic latch, and a support for the bridging bar in the frame, in combination with a connector strap at one end of which the fixed contact is secured, at the other end of which the thermostatic latch is secured, and a central area of which is cut out and fastened to the frame with the button passing through the cut-out and means for adjusting the thermostatic latch comprising a cross-plate on the frame, a screw having its head engaged in the crossplate and an arm secured to the thermostatic latch, through which arm the shank portion of the screw is threaded to bend the connector strap.

9. A trip-free circuit breaker having an insulating twopart frame comprising telescoping casings, a contact fixed in the inner frame casing, a bridging bar for connecting the fixed contact, a pair of separable members, a manually operable wedging member acting between the separable members to separate them and to close the contacts, resilient means for moving the separable members together and a thermostatic latch for locking the first of the separable members against movement away from the second, and a link connected at one end to the wedging member, in combination with a connector strap, at one end of which one fixed contact is secured, at the other end of which the thermostatic latch is secured and a central area of which is out out and fastened to the frame, a button connected to the other end of the link and slidingly mounted in the frame through the cut-out of the connector strap, means for adjusting the thermostatic latch, comprising a screw and an arm connected to the connector strap, the shank of the screw being threaded in the arm and the head of the screw being engaged in the inner casing of the frame inside the outer casing to conceal it, and means in line with the length of the button for securing the telescoping casing together.

10. A trip-free circuit breaker having an insulating twopart frame comprising inner and outer telescoping frame casing, the inner frame casing having mounted therein a pair of fixed contacts, a bridging bar for connecting the Xed contacts, a pair of separable members, one of which is yadapted to move the bridging bar for closing the contact, resilient means for moving the separable members together, land a thermostatic latch for locking the other or" said separable members against movement away from said one separable member, in combination with a manually operable wedging member acting between the separable members to separate them and to close the contacts, link means connected at one end to the wedging member, and a button connected to the other end of the link means, the outer frame casing having an aperture through which said button extends outside of the frame.

11. A trip-free circuit breaker having an insulating twopart frame comprising inner and outer telescoping frame casings, the inner frame casing having mounted therein a pair of fixed contacts, a bridging bar for connecting the fixed contacts, a pair of separable members, one of which is adapted to move the bridging bar for closing the contacts, resilient means for moving the separable members together, a thermostatic latch for locking the other of said separable members against movement away from said one separable member, and a connector strap having a central aperture, said strap extending between one of said iiXed contacts and said thermostatic latch, in combination with a manually operable wedging member acting between the separable members to separate them and to close the contacts, link means connected at one end to the Wedging member and proportioned to prevent passage of said means through said connector strap aperture, and a button connected to the other end of the link means and extending through said connector strap aperture, the outer frame casing having an aperture through which said button extends outside of the frame.

12. A trip-free circuit breaker according to claim 11, wherein the inner frame casing is substantially U-shaped, and wherein a pin passes through and extends crosswise of the telescoping casings in line with said button and said outer casing aperture for securing the casings together.

References Cited in the le of this patent UNITED STATES PATENTS 2,287,875 Grober June 30, 1942 2,613,296 Wood Oct. 7, 1952 2,813,168 Mascioli et al. Nov. 12, 1957 2,833,888 Bessiere May 6, 1958 l i a 

